This invention relates to a process for isolating microbiologically active material such as bacteria.
Presently, there are available a wide variety of apparatus for isolating relatively large microbiologically active materials such as cells on the basis of a measured physical characteristic of the cell which in turn has relavance to the biological nature of the cell. Generally, these apparatus operate by first forming a stream of cells suspended in a liquid wherein the cells are sufficiently diluted and the stream is sufficiently small such that the cells pass by a point along the flow stream path one by one. Means are provided along the flow path to sense a physical characteristic of the cell which provides a measure of a particular desired biological characteristic of the cell. Examples of such physical measurements include light scattering, electrical impedance, fluorescence intensity, light absorption or fluorescence polarization. The stream of cells passes by the means for measuring the cell physical characteristic which measurement means is adapted to control flow of the cell stream so that the individual cells characterized by a physical measurement within a desired range can be separated and isolated from the stream. In one class of class of such apparatus, a portion of the cell stream is diverted into a secondary stream such as with a syringe. In another class of such apparatus, the cell stream is divided into droplets each of which has a high probability for containing none or a single cell. The droplets are formed by any conventional means such as a piezoelectric crystal and the droplets containing the desired cells are charged electrically while the remaining droplets are uncharged so that the charged droplets can be isolated from the remaining droplets such as with a set of conventional deflection plates. The charged droplets so recovered contain the desired cells at a far higher concentration that in the original stream.
Rotman, Proceedings National Academy of Sciences, Vol. 47, pgs. 1981-1991, 1961 discloses the formation of water droplets in oil which droplets contain a small number, often one, of enzymes. However, this procedure is very tedious, difficult to replicate and the enzymes are susceptible to migration from the droplets to the oil-water interface.
While the present procedures have been highly satisfactory for concentrating animal cells of desired characteristics, these procedures have not been as satisfactory for isolating biological material of a smaller size than animal cells, such as bacteria or enzymes. This is because the physical characteristics of these smaller colume particles or molecules are much more difficult to measure accurately, particularly at the flow rates available with present cell sorters. Accordingly, it would be highly desirable to provide a means for concentrating and isolating materials having microbiological activity which materials have a size much smaller than the normal size of eucaryote cells even on a molecular size basis. Furthermore, it would be desirable to provide such a process wherein a microbiologically active molecule cell or the like having an activity of interest can be isolated alone from a large population of similar microbiologically active materials.